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A Gram-positive, aerobic, non-motile actinomycete (strain MS 3/20) was isolated from the sediment of the Sundarbans mangrove forest in India. On International Streptomyces Project (ISP) medium 2, the isolate produced yellowish brown to red aerial hyphae that carried spiny-surfaced spores in a retinaculum-apertum arrangement. Whole-cell hydrolysate of the strain contained LL-diaminopimelic acid and galactose. Predominant menaquinones were MK-9(H) and MK-9(H). Diagnostic polar lipids were glycolipid, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, unidentified phospholipid and unidentified amino lipid. The major fatty acids were anteiso-C (17.53%), iso-C (23.89%) and anteiso-C (10.29%). The strain showed 100% 16S ribosomal RNA (rRNA) gene sequence similarity with Streptomyces variabilis NBRC 12825, Streptomyces erythrogriseus LMG 19406, Streptomyces griseoincarnatus LMG 19316 and Streptomyces labedae NBRC 15864. However, strain MS 3/20 could be distinguished from these and seven other closely related species based on low levels of DNA-DNA relatedness (27.2-53.8%), supported by the unique banding pattern obtained from random amplified polymorphic DNA-PCR amplification and the distinctive matrix-assisted laser desorption/ionization-time-of-flight/mass spectrometry (MALDI-TOF/MS) profile of whole-cell proteins acquired for strain MS 3/20 in comparison with its phylogenetic relatives. Disparate morphological, physiological and chemotaxonomic features, principally growth in NaCl, further corroborated the distinction of strain MS 3/20 from other phylogenetic relatives. Strain MS 3/20 is therefore suggested to be a novel species of the genus Streptomyces, for which the name Streptomyces euryhalinus sp. nov. is proposed. The type strain is MS 3/20 (=CICC 11032=DSM 103378).

The existing techniques for detection of polyhydroxyalkanoates (PHA) in halophilic archaea/bacteria are either imprecise or require prior PHA production before screening. The proposed method involves amplification of the approximately 280-300 bp conserved region of Class III PHA synthase (phaC) gene of halophiles using the primers codehopCF and codehopCR (Han et al. Appl Environ Microb 76:7811-7819, 2010). In this study, the best reaction condition was ascertained after repeated trials. This developed method was tested on nine haloarchaeal and halobacterial type strains and 28 environmental halophilic archaea and bacteria isolated from the salt pans of the east and west coasts of India. 29 strains were found to be phaC-positive, while eight were found to be phaC-negative although they appeared PHA positive through conventional Nile Red staining. 16S rRNA-based phylogenetic analysis identified 9 haloarchaeal and 9 halobacterial species as novel PHA producers. Multiple sequence alignment of the phaC gene-derived amino acid sequences showed that only 7 amino acid residues were conserved within all four classes of phaC enzymes, whereas 61 amino acids were identical among the phaC enzyme specific to the haloarchaeal and halobacterial strains presently investigated. All phaC-positive strains produced PHA in standard nutrient deficient medium, whereas the phaC-negative strains did not accumulate any PHA as detected by gas chromatography and nuclear magnetic resonance analyses, thus proving the precision of the developed method and elimination of false positives seen with the traditional Nile Red staining procedure.

Taxonomic characterization by a polyphasic approach was carried out on two cyanobacteria, AP17 and AP24 isolated from soil biofilms of two separate islands, Lothian and Sagar respectively, of the Indian Sundarbans. The strains were studied morphologically by light microscopy, scanning and transmission electron microscopy. Growth responses to various salinities were recorded. Molecular data included sequencing and phylogenetic study of the 16S rRNA gene as well as analysis of the 14 regions of the 16S-23S ITS regions. Morphologically the strains were found to be non-heterocytous, having attenuated trichomes with a narrow, bent terminal cell without any crosswalls. Strains under investigation shared 99–100% 16S rRNA gene sequence similarity with Oxynema thaianum CCALA960, the type species of the novel Oxynema genus, recently separated from the Phormidium-Group I genus. However, cross walls in the apical portion of AP17 and AP24 were totally absent while the same was present in CCALA960. Additionally, optimal growth of AP17 and AP24 was recorded in 5–8% salinity and salinity above 14% inhibited growth of both strains, which were isolated from an intertidal environment; whereas O. thaianum CCALA960 which was found in a hypersaline environment could grow at 40% salinity. Insertion of 9 nucleotides in the D2 with spacer region, insertion of 2 nucleotides in the pre Box B spacer region, deletion of 2 nucleotides in the post Box B spacer region, deletion of 8 nucleotides in the D4 region, deletion of 8 nucleotides in V3 region and insertion of 2 nucleotides in the D5 region of the ITS sequences of AP17 and AP24 were observed in comparison to the analogous regions of CCALA960. Structural details of Box B helices of AP17 and AP24 revealed that although their lengths were identical with the reference, their sequences were completely different from CCALA960. Four nucleotide substitutions were observed in different positions in the Box B helix of O. thaianum CCALA960. Secondary structures of the V3 regions of AP17 and AP24 (containing 51 nucleotides) showed a small terminal bulge and a bigger bilateral bulge while the analogous structure of O. thaianum CCALA 960 (comprising of 59 nucleotides) showed one additional bilateral bulge in comparison to AP17 and AP24. Therefore, based on morphological, ecological and molecular differences in comparison to O. thaianum CCALA960, isolates AP17 and AP24 should be considered as a second novel species in the Oxynema genus, for which the name Oxynema aestuarii sp. nov. is proposed.

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